The objectives of this research proposal are to determine serum levels of protein SAA in neoplastic diseases, relate these data to diagnosis and prognosis, and define the relationship between this protein and the immune dysfunctions noted in cancer. Specifically studies are planned to determine if SAA is synthesized by neoplastic cells or is a factor synthesized as a reaction to a neoplasm. SAA is a serum alpha globulin known to be present in increased amounts in inflammatory diseases as well as in cancer. It has previously been shown to suppress the in vitro formation of antibody by CBA/J murine splenic lymphocytes. Sera will be collected from patients with cancer of lung and gastrointestinal tract and SAA levels determined by radioimmunoassay. SAA levels will be correlated with histologic type of tumor, presence of metastases, response to therapy and recurrence of tumor. The relationship of SAA levels to abnormalities in lymphocyte function will be determined by measuring the PBL response to mitogens and the in vivo production of antibodies to tetanus toxoid in these patients. The effect of SAA on the in vitro anti SRBC response of human peripheral blood lymphocytes (PBL) will be characterized using a system currently in use in this laboratory. PBL are cultured with SRBC antigen and the plaque forming cells enumerated by the Jerne assay four days later. Purified human SAA will be added to cultures of PBL in varying concentrations and the effect on response to SRBC measured by hemolytic plaque assay. The objective of these studies are: 1) to further characterize the suppression of immune function by SAA, 2) correlate this with the in vivo SAA level, and 3) determine whether neoplastic cells synthesize SAA.